In the case of words that the Tathagata
knows to be unfactual, untrue, unbeneficial,
unendearing and disagreeable to others,
he does not say them.– Sakyamuni Buddha
(Abhaya Sutta)
[Citta was the model Buddhist layman whose learning and behaviour the Buddha urged others to emulate…] Citta was not just able to teach the Dharma, he was also able to demonstrate its superiority over other doctrines. Once Nigantha Nataputta [Mahavira], the founder of Jainism and one of the most well-known religious teachers of the time, arrived in Macchikasanda with a large number of his disciples. Citta went to meet Nataputta who, knowing he was a disciple of the Buddha, asked him, “Do you believe, as the Buddha teaches, that it is possible to attain a meditative state where all thought stops?” “No,” answered Citta, “The Buddha teaches this but I do not believe it.”
Surprised and pleased that Citta seemed to be saying that he doubted some of the Buddha’s teaching, Nataputta looked around at all his disciples saying as he did, “See what a straightforward and clever person Citta is. Anyone who could believe in a meditative state where all thought stops might just as well believe that the mind can be caught in a net or that the Ganges can be stopped flowing by using the hand.”
When he had finished, Citta asked: “What is better, venerable sir, to know or to believe?” “Knowledge is far better than belief,” replied Nataputta. “Well, I can attain that meditative state where all thought ceases. So why should I believe what the Buddha says is true. I know it is true.”
Annoyed at being caught out, Nataputta again looked around at his disciples and said: “See what a cunning, deceitful and crooked person this Citta is.” Remaining calm and unruffled by this outburst, Citta said: “If your first statement is true [that I am straightforward and clever], then your second one must be false, and if your second statement [that I am cunning, deceitful and crooked] is true then your first one must be false,” and having said that he got up and left, leaving Nataputta struggling for a reply. (S,IV:299)
The Buddha and His Disciples: https://www.buddhanet.net/e-learning/buddhism/disciples14.htm
Ven. S. Dhammika